Unvealing newly discovered small molecules as ACE2-spike inhibitors against SARS-CoV-2.

For the fifth consecutive year since 2019, the global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections persists, resulting in a growing number of coronavirus disease 2019 (COVID- 19) cases worldwide. The primary objective for scientists worldwide is to identify at least one potent antiviral agent capable of effectively halting or disrupting SARS-CoV-2 transmission, cellular entry, replication, and pathogenicity, in the ongoing battle against the resilient COVID-19 disease. However, the arsenal of agents primarily addressing the anti-replication requirements remains limited. Notably, compounds featuring nitrogen-based heterocyclic aromatic cores in their structures, such as nucleoside-like compounds (nucleoside analogs), oxadiazoles, thiadiazoles, triazoles, quinolines, isoquinolines, and certain polyphenolics, have shown significant promise as SARS-CoV-2 inhibitors. 1 Among these, the FDA- approved medications molnupiravir and nirmatrelvir stand out. RNA-dependent RNA-polymerase, which has no counterpart in human cells, is an excellent target for drug development. 2 Small molecules targeting RdRp are suitable for different motives: - RdRps inhibitors holds the potential of activity against various viruses because the target is conserved and unlike protease inhibitors, exhibit broader activity because not all viruses encode a protease; - Polymerases present a high natural genetic barrier to drug resistance due to their conserved nature, making polymerase inhibitors a promising option for developing broad-spectrum antiviral agents; - The current therapy against RdRp lacks small molecules because most of the inhibitors are nucleos(t)ide analogues administrated by iv (e.g. Remdesivir) or orally even if they showed several side effect (e.g. Molnupiravir). For this reason, we decided to invest our effort for the identification of novel nitrogen-based small molecules targeting. In this regard, we conducted an extensive screening of previously synthesized in-house antiviral compounds. Our focus was primarily on non-nucleos(t)idic compounds featuring a central nitrogen core. Following this preliminary screening, several compounds underwent testing using the RdRp SARS-CoV-2 Primer-elongation assay on PAGE. Among those exhibiting residual enzymatic activity below 50% (up to 30 μM) post-treatment, the SARS-CoV-2 RdRp IC 50 ± SD (μM) was determined. Remarkably, some compounds displayed noteworthy in vitro activity, with IC50 values similar to the control drug, Simeprevir. Concurrently, we designed and synthesized novel derivatives that are presently undergoing biological evaluation. In this way we can elucidate structure-activity relationships (SARs) and obtaining a novel series of nitrogen-based compounds to test against other viral RdRps. The findings from this screening will be presented and discussed.